It's widely known that brake plays an important role in insuring safety in railway transportation. Brake of train in countries worldwide basically adopts air brake facilities, and the brake air is put through by pneumatic pipes installed on the train. An angle cock serves as an important part on a main brake pipe of a locomotive and rolling stock, which is installed on both ends of the main brake pipe of the locomotive and rolling stock and mounted with a brake hose. A connector with a seal rubber ring at the other end of the brake hose is used to connect the locomotive and the rolling stock or interconnect the rolling stocks. During the work of train dismantling, train formation or train maintenance and replacement of the seal ring of the connector, the air path between the main brake pipe and the brake hose need to be frequently switched on and off by means of the angle cock. Closing of the angle cock due to work requirements is defined as “Normal Closing”, while closing of it (or half-closed state) strictly prohibited during the whole running period after train formation is defined as “abnormal closing”. Once the abnormal closing of angle cock occurs, the train brake cannot be controlled by the driver, which could lead to serious accidents such as train collision, brake defect and capsizal. A technique which prevents from abnormal closing of angle cock is called “Anti-closing Technology”. Main factors causing abnormal closing of angle cock are categorized into the following four kinds: 1. entangling of rope and of the cloth tent cause the handle move which result in the cock core to be in the half-closed or in full-closed state; 2. climbing of the train by the escorts and wanderers as well as random switching lead to the half-closed or full-closed state; 3. man-made mistakes sometimes cause angle cock fully closed; 4. carelessness of the inspectors leads to the two adjacent angle cocks double-closed, single-closed or half-closed.
In order to avoid damages triggered by abnormal closing, board studies have been done on “Anti-closing Technology” both at home and abroad. Integrated analysis shows that all the research schemes can be basically divided into three kinds. The first scheme is to install a locking spring at the handle's top or adopting method of compression locking based on the traditional angle cock, or at most cases improve the air bleed brake. The above-mentioned schemes adopt a traditional method of switching to-and-fro within 90° range at close or open state or directly bleeding pressure air to the atmosphere, which fails to achieve objective of the expected design. The angle cock can only preset unified and fixed air bleed capacity only when manufactured. Obviously, any fixed air bleed capacity set in all the traditional design schemes fails to meet the requirements of different air bleed capacity of front, middle and rear cars of the train and technical requirements of different positions like front or rear part of train. A technological difficulty of greater attenuation value occurs during the inverted transmission of a brake wave and an air wave under the state of supplemented wind pressure at the front-end of the train, which makes it hard to realize the long-distance transmission. When faced with this technological difficulty, people solve it by treating it as a problem of insufficient air bleed capacity. Moreover, in accordance with theory of “when implementing air brake, the cross-section area of an air bleeding hole of the angle cock must be equal to or greater than that of locomotive air intake hole”, there is a plurality of research schemes on “great air bleed capacity”. After searching among Chinese patents, a Chinese Patent CN93214462.4 with a title of “Angle Cock with Double Ball-shaped Cores” fails to solve a problem in schemes of “great air bleed capacity”, that is, when closing angle cock, the pressure will be inevitably bled so that the angle cock is out of control, which imposes difficulties on routine work. The reason is as follows: under the condition of normal opening, the cock must be opened slowly to avoid the problem that high-pressure gas at one end of cock rushes to the other end with low-pressure gas and results in breaching of limits of pressure drop. All those “great air bleed capacity” schemes adopt traditional method of to-and fro switching within 90° range to switch on/off the angle cock. It will inevitably trigger sensible parts of train brake system when opening and finally result in bleeding pressure air in brake main pipe of the whole train including locomotive, which will seriously influence punctual departure of the train. The inventor of the present application used to have an invention patent No. CN96115748.8 with a title of “Anti-closing Unidirectional Linked Angle Cock”, anti-closing measure of which is to adopt great air bleed capacity to bleed air at one end of the hose to achieve air brake. The results of research show that when bleeding pressure air at one end of hose, brake wave still cannot be transmitted to cars near locomotive by following direction inverted with that of air wave even with increased air bleed capacity. Prior to enforcement of service brake on remote cars and locomotives by brake wave, the pressure drop near the closed angle cock has broken the maximum limit of service brake, and triggered unconventional brake to bleed pressure of brake main pipe rapidly, which causes great difficulties to routine work and seriously influences punctual departure of the train. This measure not only fails to automatically get rid of influences of entangling of rope and tent cloth as well as climbing by wanderer and escort, also doesn't conduct research or take any preventive measures towards accidents caused by carelessness of maintainers. In the latter Chinese invention patent, the solution for slowly opening of angle cock under normal operation as well as that for the problem that pressure of the brake main pipe is bled to 0 MPa when the air bleed for the second time triggers unconventional brake during maintaining work are not investigated. In this case, the angle cock provided by the latter invention patent fails to achieve technological standard for application.
The second kind of scheme is to install mechanical locking or pressure locking facilities on rolling stocks. But, it's needed to refit the existing rolling stocks, and the evaluation and forecast of preventive effects are not proved to be ideal, so the second kind of scheme is not applicable in practice. The third kind of scheme is to provide various kinds of electronic monitoring devices, but with low reliability, delayed alarming and as well as the problems of service life, economic benefits, maintenance and management. With continue improvement of air-tightness at train brake system, delayed alarm is becoming more serious. Even an alarm signal is sent out, serious consequence could not be fully avoided. Also it is hard to fight against intended damages, particularly prosecuted by the internal staff. It is unrealistic and against economic principle of tracing and monitoring the whole operational proceeding of the running train just for the purpose of preventing chance of accident, which could result in the huge waste of money and resources.